source: Dev/branches/jos-branch/server/classes/models/Answer.php @ 268

<?php
// Survey database interface class as intermediate for storing data from the site to the RDF database 
require_once 'rdfConstants.php';
// Include RAP Library to write RDF files
include(RDFAPI_INCLUDE_DIR . "RDFAPI.php");

/**
 * Description of Answer
 *
 * @author jkraaijeveld
 */
class Answer extends ResearchToolObject {
        public static $filename = 'data/results/answers.rdf';

    public $question;
        public $values;
    
    /**
     * Constructor for an Answer object
     * @param type $uid : The uid of the Answer object.
     * @param type $question : The Question object this Answer answers.
     * @param type $values : An array of strings, containing the answers.
     */
    public function __construct($uid = null, $question = null, $values = null) {
      if(!isset($uid))
      {
            $uid = md5(uniqid(rand(), true));
      }
      $this->uid = $uid;
      $this->question = $question;
      $this->values = $values;
        }
        
        /**
         * function evaluate()
         * Evaluates the references and fills in the objects for them instead.
         */
        public function evaluate()
        {
                if(is_string($this->question))
                {
                        $result = Question::get(array("uid" => $this->question));
                        if(!isset($result[0]))
                                return false;
                        $this->question = $result[0];
                }
                return true;
        }


        /**
         * function get()
         * @param type $arguments: An array having one or more of the following elements:
         * 'uid', 'question', 'values'.
         */
    public static function get($arguments)
        {
                $model = ResearchToolObject::load(Answer::$filename);
                //Create the querystring
                $querystring = '
                        PREFIX predicates: <' . SURVEYTOOL_PREDICATES_NAMESPACE . '>
                        PREFIX resources: <' . SURVEYTOOL_RESOURCES_NAMESPACE . '>
                        SELECT DISTINCT ?uid, ?question_code
                        WHERE
                        {
                                _answer predicates:resource_type resources:answer;

                                predicates:uid ?uid ;
                                predicates:question_code ?question_code ;
                                ' . ResearchToolObject::createArguments($arguments) . '
                        }';

                //Query the model
                $results = $model->sparqlQuery($querystring);   
        //An answer can have multiple values, get all these values for the answer instances found.
                $answers = array();
                if(!empty($results))
                {
                        foreach($results as $result)
                        {
                                $answers[] = new Answer($result['?uid']->label, $result['?question_code']->label, Answer::getValues($model, $result['?uid']->label));
                        }
                }
                return $answers;
        }

        /**
         * function getValues()
         * @param type $uid : The uid of the Answer for which the values should be gotten.
         */
        private static function getValues($model, $uid)
        {
                $result = $model->findRegex("[(".$uid.")]", "[(answered)]", null);
                $iterator = $result->getStatementIterator();
                $values = array();
                while($iterator->hasNext())
                {
                        $element = $iterator->next();
                        $values[] = $element->getLabelObject();
                }
                return $values;
        } 

    /**
         * function save()
         * Saves the current object into the database.
     */
    public function save()
    {
                //If evaluation fails, some references are incorrect.
                //We shouldn't save in this case. Instead - let the user know. This function returns false if the evaluation has failed.
                //TODO: Decide how to fix invalid references graciously.
                if(!$this->evaluate()) 
                        throw new Exception('Evaluation failed.');

                //Ensure the required folder exists.
                if(!is_dir('data/results'))
                        mkdir('data/results');
                $model = ResearchToolObject::load(Answer::$filename);

        $resourceAnswer = new Resource(ANSWER.'/'.$this->uid);        
        //Remove the old value stored with the given id
        $model->subtract($model->find($resourceAnswer, null, null));
        
        //Save all the new values
        $resourceAnswerType = new Resource(ANSWER);
        $predicateRType = new Resource(RTYPE);
        $model->add(new Statement($resourceAnswer,$predicateRType,$resourceAnswerType));
        
                $answerId = new Literal($this->uid);
                $predicateId = new Resource(UID);
                $model->add(new Statement($resourceAnswer, $predicateId, $answerId));

                $questionId = new Literal($this->question->uid);
                $predicateQId = new Resource(QCODE);
                $model->add(new Statement($resourceAnswer, $predicateQId, $questionId));

                if(isset($this->values))
                {
                        foreach($this->values as $value)
                        {
                                $answerValue = new Literal($value);
                                $predicateAnswer = new Resource(ANSWERED);
                                $model->add(new Statement($resourceAnswer, $predicateAnswer, $answerValue));
                        }
                }
                $model->saveAs(Answer::$filename, 'rdf');
                return true;
        }
}

?>